[Progressive degenerative myoclonic epilepsy. Systematized olivo-cerebellar lesions].

A 15 year-old North-African female showed typical symptoms and evolution of Progressive Myoclonus Epilepsy of the Unverricht type. Pathological examination failed to show either inclusion bodies or any other storage material. The only relevant findings included degenerative changes in the inferior olives and, to a lesser extent, in the cerebellar cortex. The site of lesions was remarkable: in the inferior olives, lesions were bilaterally and symmetrically restricted to the external angles (lateral lamellae); in the cerebellum, loss of Purkinje cells and ascending fibres of the molecular layer was prominent in the lateralmost part of the hemispheres (semilunar lobules). Such a topography implies a system disorder involving the olivo-cerebellar pathway, particularly in that part which projects to the neocerebellum. Twelve other clinico-pathological cases of progressive myoclonus epilepsy of the degenerative group are reviewed. It is suggested that, here again, lesions--although more diffuse--may be related to a primarily olivo-cerebellar involvement.